It has previously been proposed to make pressure sensors of semiconductor material by so-called micromachining, involving oxidation, masking, etching and other known semiconductor processing steps; and U.S. Pat. No. 6,211,558 granted Apr. 3, 2001, and U.S. Pat. No. 6,352,874 disclose such techniques.
However, the pressure sensors of these references are not as linear as might be desired; and it would also be desirable to further reduce the size of the sensor systems.
In pressure sensor systems, the capacitance of a diaphragm type variable capacitance may be compared to a fixed reference capacitor and the resultant output provides an indication of the pressure applied to the diaphragm. U.S. Pat. No. 4,398,426 granted Aug. 16, 1983 discloses a system of this type.